The Žiežmariai synagogue in Lithuania is notable for several architectural details that set it apart:

1. Wooden Structure: As a wooden synagogue, it belongs to a unique architectural genre of Renaissance-era wooden synagogues (source).

2. Decorative Ceilings: One remarkable feature is the ceilings with boards laid in decorative herringbone patterns (source).

3. Modesty and Size: The synagogue combines modest decor with monumental size, a reflection of its era's architectural styles (source).

4. Prayer Hall: The lofty southeastern part of the building houses a prayer hall and features 18 windows, many of which were integrated with doors (source).

5. Women’s Balcony: Like many traditional synagogues, it includes a women's balcony. This is an architectural timber structure that has been preserved and recently renovated (source).

6. Historical Importance: Besides its architectural value, the synagogue also holds historical significance, serving as a Holocaust site and a testament to the Jewish heritage in the region (source).

Here are some images of the Žiežmariai synagogue:

These features combine to make the Žiežmariai synagogue a unique and important architectural monument in Lithuania.